Vibration motor

ABSTRACT

A vibration motor includes a stationary portion including a casing and a coil; a vibrator including a magnet, and at least one elastic member. The magnet is arranged on an upper side of the coil. The stationary portion includes at least one projecting portion arranged to project in the vertical direction. A portion of the at least one projecting portion is arranged opposite to a portion of the vibrator in the one direction. The at least one elastic member includes a plate spring portion arranged to support at least one of both ends of the vibrator with respect to the one direction. The plate spring portion includes a decreased width portion and an increased width portion, the decreased width portion being above or below a corresponding one of the at least one projecting portion when viewed from one side in the one direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2015-204911 filed on Oct. 16, 2015. The entire contentsof this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a vibration motor.

2. Description of the Related Art

Cellular phones and portable players often include a vibration motor asa vibration generation device to produce haptic feedback. The vibrationmotor includes a vibrator including a plate-shaped weight and a magnet,a plurality of elastic members to support the vibrator, and a coil. As arange in which the vibrator is capable of moving increases, the risk ofa break of any elastic member increases. Accordingly, the vibrationmotor typically includes a movement restriction portion arranged to makecontact with the vibrator to restrict movement of the vibrator when thevibrator moves to a large extent. Such a vibration motor is describedin, for example, U.S. Pat. No. 8,269,379.

In order to bring the movement restriction portion and the vibrator intocontact with each other, it is necessary to arrange the vibrator and themovement restriction portion to overlap with each other when viewed in adirection in which the vibrator vibrates (i.e., a vibration direction).This arrangement causes an interference between the movement restrictionportion and the elastic member. In the vibration motor described in U.S.Pat. No. 8,269,379, a total of four elastic members are arranged tosupport the vibrator, with two of the elastic members arranged on eitherside of the vibrator in the vibration direction, in order to prevent aninterference between the movement restriction portion and any elasticmember.

The vibration motor described in U.S. Pat. No. 8,269,379 is increased inthe number of components, because two of the elastic members arearranged at each of both ends of the vibrator with respect to thevibration direction. The increase in the number of components makes itdifficult to achieve a weight reduction.

In view of the above circumstances, the present invention has beenconceived to provide a vibration motor having a simple structure andcapable of limiting the range in which the vibrator is capable of movingto a specific range.

SUMMARY OF THE INVENTION

A vibration motor according to a preferred embodiment of the presentinvention includes a stationary portion including a casing and a coil; avibrator including a magnet, and supported to be capable of vibrating inone direction with respect to the stationary portion; and at least oneelastic member arranged between the stationary portion and the vibrator.The magnet is arranged on an upper side of the coil in a verticaldirection perpendicular to the one direction. The stationary portionincludes at least one projecting portion arranged to project in thevertical direction. A portion of the at least one projecting portion isarranged opposite to a portion of the vibrator in the one direction. Theat least one elastic member includes a plate spring portion arranged tosupport at least one of both ends of the vibrator with respect to theone direction. The plate spring portion includes a decreased widthportion and an increased width portion having a vertical width greaterthan a vertical width of the decreased width portion, the decreasedwidth portion being above or below a corresponding one of the at leastone projecting portion when viewed from one side in the one direction.

The vibration motor according to the above preferred embodiment of thepresent invention has a simple structure, and is able to limit the rangein which the vibrator is capable of moving to a specific range.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a vibration motor according toa first preferred embodiment of the present invention.

FIG. 2 is a perspective view of the vibration motor according to thefirst preferred embodiment of the present invention.

FIG. 3 is a top view of the vibration motor according to the firstpreferred embodiment of the present invention.

FIG. 4 is a side view of the vibration motor according to the firstpreferred embodiment of the present invention.

FIG. 5 is a side sectional view of the vibration motor according to thefirst preferred embodiment of the present invention.

FIG. 6 is a side view of the vibration motor according to the firstpreferred embodiment of the present invention.

FIG. 7 is a perspective view of a columnar member according to the firstpreferred embodiment of the present invention.

FIG. 8 is a perspective view of a base according to the first preferredembodiment of the present invention.

FIG. 9 is a perspective view illustrating a coil fitted to the baseaccording to the first preferred embodiment of the present invention.

FIG. 10 is a side sectional view of a vibration motor according to asecond preferred embodiment of the present invention.

FIG. 11 is a side sectional view of a vibration motor according to athird preferred embodiment of the present invention.

FIG. 12 is a side sectional view of a vibration motor according to afourth preferred embodiment of the present invention.

FIG. 13 is a perspective view of elastic members and a weight providedin a vibration motor according to a fifth preferred embodiment of thepresent invention when viewed from the lower side.

FIG. 14 is a perspective view of the elastic members provided in thevibration motor according to the fifth preferred embodiment of thepresent invention when viewed from the lower side.

FIG. 15 is a perspective view of a vibration motor according to a sixthpreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. First PreferredEmbodiment

Hereinafter, exemplary preferred embodiments of the present inventionwill be described with reference to the accompanying drawings. FIG. 1 isan exploded perspective view of a vibration motor according to a firstpreferred embodiment of the present invention. FIG. 2 is a perspectiveview of the vibration motor according to the first preferred embodimentof the present invention. FIG. 3 is a top view of the vibration motoraccording to the first preferred embodiment of the present invention.FIG. 4 is a side view of the vibration motor according to the firstpreferred embodiment of the present invention. Each of FIGS. 2, 3, and 4illustrates the vibration motor with a cover thereof removed therefrom.

In each of FIGS. 1 to 4, the right-left direction is defined as onedirection, which is denoted as an X direction. Meanwhile, a verticaldirection, which is a direction perpendicular to the one direction, isdenoted as a Y direction. For example, the upper side in FIG. 1 is theupper side in the vertical direction (i.e., the Y direction). The sameis true of the other drawings. It should be noted, however, that theabove definitions of the directions are not meant to restrict in any waythe orientation of a vibration motor according to any preferredembodiment of the present invention.

1.1 Overall Structure

A vibration motor 100 according to the present preferred embodimentincludes a base 10, a coil 50, a vibrator 20, an elastic member 30, anelastic member 31, and a cover 40. The base 10 includes a base portion11, a board 12, and a columnar member 62. The vibration motor 100includes a casing including the base portion 11 and the cover 40. Theboard 12 may be either a rigid board or a flexible board. The coil 50 isfitted to an upper surface of the base 10 (this fitting will bedescribed in detail below). That is, the vibration motor 100 includesthe vibrator 20, the elastic member 30, and a stationary portionincluding the base 10, the coil 50, and the cover 40. That is, thestationary portion includes the casing and the coil 50.

The vibrator 20 includes a weight 21 and magnets 22. Each magnet 22 isarranged in a cavity portion 213 defined in the weight 21. That is, eachmagnet 22 is held by the weight 21. Each magnet 22 is arranged on theupper side of the coil 50. That is, the vibrator 20 includes the magnets22. Each magnet 22 is arranged on the upper side of the coil 50 in thevertical direction (i.e., the Y direction).

As described in detail below, one end of the elastic member 30 is fixedto the weight 21, while an opposite end of the elastic member 30 isfixed to an inner wall surface of the cover 40. That is, the elasticmember 30 is arranged between the stationary portion and the vibrator20. The other elastic member is fixed in a manner similar to the mannerin which the elastic member 30 is fixed. The vibrator 20 is thussupported by the elastic members 30 and 31 such that the vibrator 20 iscapable of vibrating in the one direction (i.e., the X direction) withrespect to the stationary portion. The coil 50, the vibrator 20, and theelastic members 30 and 31 are arranged in an interior space defined bythe cover 40 and the base 10.

A magnetic field is generated around the coil 50 as a result of the coil50 being energized through an electrical circuit on the board 12. Themagnetic field generated around the coil 50 interacts with magneticfields generated by the magnets to cause reciprocating vibration of thevibrator 20 in the one direction.

1.2 Structures of Elastic Member and Vibrator

Next, the elastic member 30 and the vibrator 20 will now be described indetail below. The elastic member 31 is similar in structure to theelastic member 30, and a description of the elastic member 31 istherefore omitted.

The elastic member 30 includes a plate spring portion 32, a fixingportion 33, a connection portion 34, and a top plate portion 35, andthese portions are joined to one another. The plate spring portion 32includes beam portions 321 and 322 and a joining portion 323. Thejoining portion 323 joins one end portion of the beam portion 321, whichis in the shape of a plate, and one end portion of the beam portion 322,which is in the shape of a plate, to each other. That is, the platespring portion 32 includes the plurality of beam portions 321 and 322and the joining portion 323.

The elastic member 30 includes the plate spring portion 32, which isarranged to support at least one of both ends of the vibrator 20 withrespect to the one direction (i.e., the X direction).

The fixing portion 33 includes a first wall portion 331 arranged toextend perpendicularly to the one direction (i.e., the X direction) ofthe vibrator 20, and a second wall portion 332 joined to the first wallportion 331 and arranged to extend along the one direction of thevibrator 20. One end of the first wall portion 331 is joined to anotherend of the beam portion 322. An opposite end of the first wall portion331 is joined to one end of the second wall portion 332. An opposite endof the second wall portion 332 is joined to the top plate portion 35through the connection portion 34. Note that, instead of the second wallportion 332, the first wall portion 331 may alternatively be joined tothe top plate portion 35 through the connection portion 34. Also notethat each of the first and second wall portions 331 and 332 may bejoined to the top plate portion 35 through the connection portion 34.The top plate portion 35 is arranged to have an area greater than thearea of the fixing portion 33.

The weight 21 includes a first weight portion 211 and second weightportions 212 a and 212 b. The first weight portion 211 is in the shapeof a rectangular parallelepiped. The second weight portions 212 a and212 b are arranged at both ends of the vibrator 20 with respect to theone direction, and are arranged to extend downward from a lower surfaceof the first weight portion 211.

The second wall portion 332 is fixed to a surface defined by sidesurfaces of the first weight portion 211 and the second weight portion212 a which extend in the one direction. The first wall portion 331 isfixed to a surface defined by side surfaces of the first weight portion211 and the second weight portion 212 a which extend in the directionperpendicular to the one direction. That is, both the first and secondwall portions 331 and 332 are fixed to a side surface of the vibrator20. This fixing may be accomplished by, for example, welding or adhesionusing an adhesive. In the case where the wall portion is fixed by spotwelding performed on a peripheral portion of the wall portion, forexample, the wall portion is directly fixed to the side surface of thevibrator. In the case where the wall portion is fixed by using theadhesive, for example, the wall portion is indirectly fixed to the sidesurface of the vibrator with the adhesive therebetween.

The top plate portion 35 is fixed to an upper surface of the firstweight portion 211. This fixing may be accomplished by, for example,welding or adhesion using an adhesive. In the case of welding, spotwelding may be performed on a peripheral portion of the top plateportion 35, for example. The top plate portion 35 is arranged oppositeto the magnet 22 in the vertical direction.

The elastic member 31 is similar in structure to the elastic member 30.A connection portion (which corresponds to the connection portion 34 ofthe elastic member 30) of the elastic member 31 is fixed to the weight21 at a position diagonally opposite to the connection portion 34 at anupper surface of the weight 21. That is, the vibration motor 100 isprovided with the two elastic members 30 and 31. Each of the two elasticmembers 30 and 31 is arranged to support a separate one of both the endsof the vibrator 20 with respect to the one direction (i.e., the Xdirection).

The fixing of the fixing portion 33 to the side surface of the vibrator20 and the fixing of the top plate portion 35, which is joined to thefixing portion 33, to the upper surface of the vibrator 20 as describedabove contribute to preventing the vibration of the vibrator 20 fromcausing a detachment of the fixing portion 33 or the top plate portion35 from the vibrator 20 or a break of the fixing portion 33 or the topplate portion 35. In addition, the joining of the fixing portion 33 andthe top plate portion 35 through the connection portion 34 furtherincreases the above effect. In addition, the fixing portion 33 is fixedto both the first weight portion 211 and the second weight portion 212a, and this increases the strength with which the elastic member 30 isfixed to the vibrator 20.

Note that not both but only one of the first and second wall portions331 and 332 may be fixed to the vibrator 20.

The elastic member 30 is made of, for example, SUS632J1, which is aferromagnetic spring material. That is, at least a portion of the topplate portion 35 is made of a ferromagnetic material. The top plateportion 35 is thus able to serve as a back yoke for the magnet 22. Notethat the elastic member 30 may not necessarily be made of aferromagnetic material, and that, alternatively, an upper surface of thetop plate portion 35 may be coated with a ferromagnetic material.

The top plate portion 35 includes a through hole 351 passingtherethrough in the vertical direction. The first weight portion 211includes the cavity portions 213, each of which passes therethrough inthe vertical direction. The magnets 22 are arranged in the cavityportions 213. That is, the through hole 351 is arranged opposite to boththe corresponding cavity portion 213 and the corresponding magnet 22 inthe vertical direction. This allows a positioning pin to be insertedthrough the cavity portion 213, without the magnet 22 arranged therein,and through the through hole 351 to position the top plate portion 351.

Here, FIG. 5 is a side sectional view of the vibration motor 100 withthe cover 40. As illustrated in FIG. 5, a first gap is defined betweenthe top plate portion 35 and the cover 40. A magnetic fluid S1 havingviscosity is arranged in the first gap. That is, the magnetic fluid S1is arranged in a gap between the casing and a surface of the vibrator 20on the side opposite to the lower surface thereof.

In addition, a second gap is defined between an upper surface of thecoil 50 and the lower surface of the first weight portion 211 of thevibrator 20. A magnetic fluid S2 having viscosity is arranged in thesecond gap. The above arrangement allows each of the magnetic fluids S1and S2 to serve as a damper when the vibrator 20 vibrates. Moreover, themagnetic fluids S1 and S2 possess magnetism, and are thus able to stayon the top plate portion 35 and the coil 50, respectively, each of whichis made of a metal, even if the vibrator 20 vibrates. Note that only oneof the magnetic fluids S1 and S2 may be provided. In other words, themagnetic fluid may be arranged only in the first gap or only in thesecond gap.

When the weight 21 includes only the first weight portion 211, which isin the shape of a plate, a space is defined between the weight 21 andthe base 10 in the vibration motor 100. This space includes an area inwhich the coil 50 is arranged, and an area in which the coil 50 is notarranged. Addition of the second weight portions 212 a and 212 b in thearea in which the coil 50 is not arranged increases the weight of theweight 21. As illustrated in FIG. 5, each of the second weight portions212 a and 212 b is arranged opposite to the coil 50 in the onedirection. That is, an area in which the coil 50 is not arranged andwhich is near the coil 50 is used to dispose each of the second weightportions 212 a and 212 b, each of which extends downward from the firstweight portion 211. This enables an increase in the weight of the weight21 without increasing the thickness of the vibration motor 100. Thisleads to realizing a vibration motor having a small thickness and alarge inertial force.

In addition, as illustrated in FIG. 5, a vertical distance H1 betweenthe coil 50 and the first weight portion 211 is greater than a verticaldistance H2 between the second weight portion 212 a and the board 12.This contributes to preventing the first weight portion 211 fromcolliding against the coil 50 to damage the coil 50 when, for example, afall of the vibration motor 100 occurs. This effect is particularlyfavorable when the magnetic fluid S2 is not provided.

1.3 Structure to Restrict Movement of Vibrator

Next, a structure to restrict movement of the vibrator 20 will now bedescribed in detail below.

The base portion 11 includes a first projecting portion 111, which isarranged to project upward, and a second projecting portion 112, whichis arranged to project upward, on separate sides of the vibrator 20 inthe one direction. Each of the first and second projecting portions 111and 112 is arranged between the vibrator 20 and the cover 40. That is,the stationary portion includes the projecting portions 111 and 112 eachof which projects in the vertical direction. At least one firstprojecting portion 111 is arranged between the vibrator 20 and thecasing on one side of the vibrator 20 in the one direction. Further, atleast one second projecting portion 112 is arranged between the vibrator20 and the casing on an opposite side of the vibrator 20 in the onedirection.

The first projecting portion 111 is arranged at a position between thebeam portions 321 and 322. The same is true of the second projectingportion 112. The coil 50 is arranged between the first and secondprojecting portions 111 and 112.

Each of the first and second projecting portions 111 and 112 is definedby, for example, press forming. This secures a sufficient strength ofeach projecting portion. Note that the projecting portion may not be anintegral portion of the base portion 11, but may alternatively be aseparate member.

Here, FIG. 6 is a side view of the vibration motor 100 in the state ofFIG. 2 when viewed from one side in the one direction. FIG. 6illustrates a view of the vibration motor 100 when viewed from theposition between the beam portions 321 and 322. As illustrated in FIG.6, a portion of the first projecting portion 111 is opposed to a portionof the second weight portion 212 a. That is, a portion of each of theprojecting portions 111 and 112 is opposed to a portion of the vibrator20 in the one direction.

In addition, the beam portion 322 has middle portions along the lengthof the beam portion 322 cut out in the vertical direction, thusincluding a decreased width portion 325. That is, the decreased widthportion 325 is defined as a result of portions of the plate springportion 32 being cut out in the vertical direction. Further, the beamportion 322 includes increased width portions 324 on both sides of thedecreased width portion 325, each increased width portion 324 having avertical width greater than that of the decreased width portion 325.That is, the plate spring portion 32 includes the decreased widthportion 325 and the increased width portions 324.

The decreased width portion 325 is above or below the first projectingportion 111 when viewed from one side in the one direction. That is, thedecreased width portion is above or below the corresponding projectingportion when viewed from one side in the one direction. This contributesto preventing a contact between the elastic member 30 and the firstprojecting portion 111 when the vibrator 20 moves. In addition, thedecreased width portion 325, which is provided in each of the beamportions 321 and 322, allows both the ends of the vibrator 20 withrespect to the one direction to be supported by the two plate springportions 32. This contributes to limiting an increase in the number ofparts of the vibration motor 100. A similar relationship is establishedbetween the elastic member 31 and the second projecting portion 112.

In addition, as illustrated in FIG. 5, a distance L2 between the firstprojecting portion 111 and the vibrator 20 is arranged to be shorterthan an effective range L1 of motion of the vibrator 20. Here, theeffective range of motion refers to a range in which the vibrator 20 ina stationary state is capable of moving until the elastic member 30 isdeformed to a maximum extent within the elastic range thereof. Forexample, in FIG. 5, a range in which the vibrator 20 in the stationarystate is capable of moving until the plate spring portion 32 of theelastic member 30 is compressed to a maximum extent corresponds to theeffective range of motion. That is, the distance between the vibrator 20and each of the projecting portions 111 and 112 is shorter than theeffective range of motion of the vibrator 20.

Thus, if a fall of the vibration motor 100, for example, causes thevibrator 20 to move to a large extent, the vibrator 20 makes contactwith the first projecting portion 111 to be restrained from furthermovement, before moving to the limit of the effective range of motion.This contributes to more effectively preventing damage to the elasticmember 30.

The above structure for movement restriction as realized by the firstprojecting portion 111, the vibrator 20, and the elastic member 30 issimilarly realized by the second projecting portion 112, the vibrator20, and the elastic member 31. As described above, the first projectingportion 111 is arranged between the vibrator 20 and the cover 40 on oneside of the vibrator 20 in the one direction. The second projectingportion 112 is arranged between the vibrator 20 and the cover 40 on theopposite side of the vibrator 20 in the one direction. Note that aplurality of first projecting portions 111 may be arranged on the oneside of the vibrator 20 in the one direction, and a plurality of secondprojecting portions 112 may be arranged on the opposite side of thevibrator 20 in the one direction. Also note that a projecting portion(s)may be arranged on only one side of the vibrator 20 in the onedirection.

In addition, as illustrated in FIG. 5, a distance L3 between the secondweight portion 212 b and the coil 50 as measured in the one direction isgreater than the distance L2 between the second weight portion 212 a andthe first projecting portion 111. This prevents the second weightportion 212 b from coming into contact with the coil 50 when thevibrator 20 moves to such an extent that the second weight portion 212 ais brought into contact with the first projecting portion 111. Thiscontributes to preventing damage to the coil 50. The same is true of therelationship between the distance L3 between the second weight portion212 a and the coil 50 as measured in the one direction, and the distancebetween the second weight portion 212 b and the second projectingportion 112. Thus, a large movement of the vibrator 20 to either side inthe one direction would not cause damage to the coil 50.

1.4 Structure for Positioning Coil

Next, the structure for positioning the coil 50 in the vibration motor100 will now be described in detail below. As illustrated in FIG. 1, thebase portion 11 includes a first columnar portion 61 arranged to projectupward to assume the shape of a plate. The first columnar portion 61includes a recessed portion 611. As shown in a perspective view of FIG.7, the columnar member 62 includes a second columnar portion 621, whichis in the shape of a plate, and a third columnar portion 622 arranged toproject to assume a columnar shape and made of the same material as thatof the second columnar portion 621.

The third columnar portion 622 is inserted into the recessed portion 611to bring the second columnar portion 621 into contact with the firstcolumnar portion 61 to fix the columnar member 62 to the first columnarportion 61. This fixing is accomplished by welding or adhesion using anadhesive, for example. Thus, a columnar portion 60 includes the firstcolumnar portion 61 and the columnar member 62. That is, the base 10includes the columnar portion 60, which is arranged to project upward inthe vertical direction perpendicular to the one direction. In addition,the board 12 includes a board through hole 121 passing therethrough inthe vertical direction. The columnar portion 60 is inserted in the boardthrough hole 121. The board 12 is thus positioned on and fixed to thebase portion 11. This situation is illustrated in a perspective view ofFIG. 8.

Then, as illustrated in a perspective view of FIG. 9, the coil 50 isfixed to the board 12 with an outside surface of the columnar portion 60arranged opposite to an inside surface of the coil 50, which is annular.At this time, a double-sided tape is stuck to a lower surface of thecoil 50, for example, and the coil 50 is pressed against the board 12.The above structure allows the coil 50 to be easily positioned withoutuse of a jig, increasing efficiency in fitting of the coil 50.

An upper end surface of the columnar portion 60 is arranged at a levellower than that of an upper end surface of the coil 50. Thus, in thecase where an adhesive having a relatively high fluidity is applied tothe lower surface of the coil 50 and the coil 50 is pressed against theboard 12 to fix the coil 50, for example, a surface of the adhesive isdefined between the upper end surface of the columnar portion 60 and theinside surface of the coil 50 if the adhesive flows from the lowersurface of the coil 50 into a gap between the inside surface of the coil50 and the outside surface of the columnar portion 60 and further ontothe upper end surface of the columnar portion 60. This contributes topreventing the adhesive from being attached to the upper end surface ofthe coil 50.

Because no jig is used, the use of the adhesive having a relatively highfluidity would not lead to an attachment of the adhesive to a jig andallowing the jig to attach the adhesive to an upper surface of a nextcoil in an operation of fitting the next coil.

The adhesive arranged in the gap between the inside surface of the coil50 and the outside surface of the columnar portion 60 as described aboveincreases the strength with which the coil 50 is fixed in the verticaldirection. In addition, the columnar portion 60 is made up of threemembers, i.e., the first, second, and third columnar portions 61, 621,and 622. This increases the precision with which the columnar portion 60is formed, leading to an increase in precision in positioning the coil50.

Note that the columnar portion 60 may be modified in other preferredembodiments of the present invention. For example, the board 12 may bearranged to include a columnar portion 60 projecting upward, without theboard through hole 121 defined in the board 12.

Also note that the columnar portion 60 may be made of the same materialas that of the base portion 11. For example, the columnar portion 60 maybe defined by press working or molding. This simplifies the process ofdefining the columnar portion 60. Also note that a columnar portion 60made of a resin may be defined by an insert molding process incombination with a plate portion of a base portion 11 made of a metal.This reduces the cost of the parts.

Also note that an electronic component, such as a capacitor or atransformer, mounted on the board 12 may be used as the columnar portion60.

In the above-described first preferred embodiment, the weight 21includes the second weight portions 212 a and 212 b each of whichextends downward from the lower surface of the plate-shaped first weightportion 211. The weight, however, is not limited to this shape. Forexample, the second weight portions 212 a and 212 b may be omitted ifthe first weight portion 211 ensures sufficient vibration. In this case,a portion of each of the first and second projecting portions 111 and112 is arranged opposite to the first weight portion 211 in the onedirection.

2. Second Preferred Embodiment

Next, a second preferred embodiment of the present invention will now bedescribed below. FIG. 10 is a side sectional view of a vibration motor110 according to the present preferred embodiment (this figurecorresponds to FIG. 5, which illustrates the first preferredembodiment). In the above-described first preferred embodiment, thefirst and second projecting portions 111 and 112, which serve torestrict the movement of the vibrator 20, are arranged on the far sideof the second weight portions 212 a and 212 b, respectively, in the onedirection with respect to the coil 50 as illustrated in FIG. 5. Incontrast, in the present preferred embodiment, first and secondprojecting portions 113 and 114 are arranged between a coil 50 andsecond weight portions 212 a and 212 b, respectively, in the onedirection as illustrated in FIG. 10.

In this preferred embodiment, the first and second projecting portions113 and 114 do not interfere with elastic members 30 and 31,respectively, and this eliminates the need to define a decreased widthportion in a beam portion of each elastic member as in the firstpreferred embodiment. This leads to securing a sufficient verticaldimension of the beam portion, resulting in improved rigidity of a platespring portion 32.

3. Third Preferred Embodiment

Next, a third preferred embodiment of the present invention will now bedescribed below. FIG. 11 is a side sectional view of a vibration motor120 according to the present preferred embodiment (this figurecorresponds to FIG. 5, which illustrates the first preferredembodiment). In the present preferred embodiment, accommodating portions115 a and 115 b passing through a board 12 and a base portion 11 in thevertical direction are defined in a base 10. In addition, a portion of asecond weight portion 214 a is arranged in the accommodating portion 115a, and a portion of a second weight portion 214 b is arranged in theaccommodating portion 115 b.

According to this preferred embodiment, movement of a vibrator 20 isrestricted by a contact of the second weight portion 214 a with theaccommodating portion 115 a, or a contact of the second weight portion214 b with the accommodating portion 115 b, if the vibrator 20 moves toa large extent in the one direction. Note that each accommodatingportion may alternatively be defined by a non-through recessed portion,instead of a through hole.

4. Fourth Preferred Embodiment

Next, a fourth preferred embodiment of the present invention will now bedescribed below. FIG. 12 is a side sectional view of a vibration motor130 according to the present preferred embodiment (this figurecorresponds to FIG. 5, which illustrates the first preferredembodiment). In the present preferred embodiment, a first projectingportion 41 and a second projecting portion 42 each of which projectsdownward from an inside surface of an upper surface portion of a cover40 are provided. A beam portion of each of elastic members 30 and 31includes a decreased width portion to prevent an interference with thefirst projecting portion 41 or the second projecting portion 42. Thus,movement of a vibrator 20 is restricted by a contact of a first weightportion 211 with the first projecting portion 41 or the secondprojecting portion 42 if the vibrator 20 moves to a large extent in theone direction.

That is, the casing includes the base portion 11, which is arranged onthe lower side, and the cover 40, which is arranged to cover one surfaceof the base portion 11, and each of the projecting portions 111, 112,113, 114, 41, and 42 is made of the same material as that of at leastone of the base portion 11 and the cover 40.

5. Fifth Preferred Embodiment

Next, a fifth preferred embodiment of the present invention will now bedescribed below. FIGS. 13 and 14 are perspective views of elasticmembers 30 and 31 and a weight 21 provided in a vibration motoraccording to the present preferred embodiment when viewed from the lowerside (in FIG. 14, the weight 21 is not shown). In the present preferredembodiment, the elastic member 30 further includes a bottom plateportion 37 arranged opposite to a top plate portion 35 in the verticaldirection with a vibrator 20 therebetween. The bottom plate portion 37may be arranged to be in contact with the vibrator 20, or be arrangedopposite to the vibrator 20 with a slight gap therebetween. The bottomplate portion 37 may be fixed to the vibrator 20. The bottom plateportion 37 is joined to a lower end of a second wall portion 332 througha connection portion 36. Note that the bottom plate portion 37 mayalternatively be joined to a lower end of a first wall portion 331,instead of the second wall portion 332, through the connection portion36. Further, the bottom plate portion 37 may alternatively be joined tothe lower end of each of the first and second wall portions 331 and 332through the connection portion 36.

Because the bottom plate portion 37 is arranged opposite to the topplate portion 35 in the vertical direction with the vibrator 20therebetween, the strength with which the elastic member 30 and thevibrator 20 are fixed to each other is increased. In particular, in thecase where the bottom plate portion 37 is arranged to be in contact withthe vibrator 20, the vibrator 20 is held by portions of the elasticmember 30 from both sides in the vertical direction, and therefore, astrong impact applied to the vibration motor because of a fall of thevibration motor, for example, would not cause a detachment of theelastic member 30 from the vibrator 20. In addition, in the case wherethe bottom plate portion 37 is arranged to be in contact with thevibrator 20, the bottom plate portion 37 can be used for positioningwhen the top plate portion 35 is fixed, and this leads to increasingefficiency in fitting of the top plate portion 35.

6. Sixth Preferred Embodiment

Next, a sixth preferred embodiment of the present invention will now bedescribed below. FIG. 15 is a perspective view of a vibration motor 140according to the present preferred embodiment. In the present preferredembodiment, a buffer member is arranged between a first wall portion 331and an end surface of a vibrator 20 facing in the one direction. Thebuffer member 23 is made of an elastic material. The buffer member 23 ispreferably made of, for example, a resin material such as a silicone,urethane, a fluorocarbon resin, or an acrylic resin, or a material thatdamps vibration, such as a damping material, such as αGEL.

Because the buffer member 23 is arranged between the first wall portion331 and the end surface of the vibrator 20 facing in the one direction,the reciprocating vibration of the vibrator 20 can be damped. In moredetail, if supply of drive signals is stopped, the vibrator 20, whichhas a great weight, freely vibrates due to inertia in the case where thebuffer member 23 is not provided, but in the case where the buffermember 23 is provided, an interference between the vibrator 20 and theelastic member 30 produces an effect of damping action. Accordingly,when supply of electric current to a coil 50 is stopped to stop thevibration of the vibrator 20, the vibration of the vibrator 20 can bequickly stopped. Note that the buffer member 23 may be arranged in arecessed portion.

While preferred embodiments of the present invention have been describedabove, the preferred embodiments may be modified in various mannerswithout departing from the scope and spirit of the present invention.

Preferred embodiments of the present invention are applicable tovibration motors provided in, for example, smartphones or gamepads.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A vibration motor comprising: a cover; a boardincluding an electrical circuit; a stationary portion including a casingand a coil; a vibrator including a magnet, and supported to vibrate inone direction with respect to the stationary portion; and at least oneelastic member between the stationary portion and the vibrator; whereinthe magnet is above an upper side of the coil in a vertical directionperpendicular to the one direction; the stationary portion includes atleast one projecting portion that projects in the vertical direction; aportion of the at least one projecting portion is opposite to a portionof the vibrator in the one direction; a portion of the board is directlyadjacent to and partially surrounds a portion of the at least oneprojecting portion; the at least one elastic member includes a platespring portion that supports at least one of both ends of the vibratorwith respect to the one direction; and the plate spring portion includesa decreased width portion and an increased width portion having avertical width greater than a vertical width of the decreased widthportion, the decreased width portion being above or below acorresponding one of the at least one projecting portion when viewedfrom one side in the one direction.
 2. The vibration motor according toclaim 1, wherein the decreased width portion is defined as a result of aportion of the plate spring portion being cut out in the verticaldirection.
 3. The vibration motor according to claim 2, wherein theplate spring portion includes a plurality of plate-shaped beam portions,and a joining portion that joins end portions of the beam portions; andthe decreased width portion is defined in each beam portion.
 4. Thevibration motor according to claim 3, wherein the at least one elasticmember includes two elastic members; and each of the two elastic memberssupports a separate one of both the ends of the vibrator with respect tothe one direction.
 5. The vibration motor according to claim 4, whereineach of the at least one elastic member includes: a fixing portion fixedto a side surface of the vibrator; and a top plate portion joined to thefixing portion, and fixed to an upper surface of the vibrator; thefixing portion includes: a first wall portion that extendsperpendicularly to the one direction of the vibrator; and a second wallportion joined to the first wall portion, and extending along the onedirection of the vibrator; and a buffer member between an end surface ofthe vibrator facing in the one direction and the first wall portion. 6.The vibration motor according to claim 1, wherein the at least oneprojecting portion includes at least one projecting portion between thevibrator and the casing on one side of the vibrator in the onedirection.
 7. The vibration motor according to claim 6, wherein the atleast one projecting portion includes at least one projecting portionbetween the vibrator and the casing on an opposite side of the vibratorin the one direction.
 8. The vibration motor according to claim 6,wherein a distance between at least one of the at least one projectingportion and the vibrator is shorter than an effective range of motion ofthe vibrator.
 9. The vibration motor according to claim 6, wherein thecasing includes a base portion on a lower side, and the cover covers onesurface of the base portion; and each of the at least one projectingportion is made of a same material as that of at least one of the baseportion and the cover.
 10. The vibration motor according to claim 9,further comprising a magnetic fluid provided in a gap between the casingand a surface of the vibrator on a side opposite to a lower surface ofthe vibrator.
 11. The vibration motor according to claim 1, wherein theportion of the board includes a notch which is directly adjacent to andpartially surrounds the portion of the at least one projecting portion.